Thanks @Antonio!
Not to raise any alarms, as we dont know the history of your engine, but the fact that 3 AND 4 are both hi, clues me into mentioning that both intake valves on your engine share the same cam lobe. Also someone noted that the egt spread of 150 seemed high? Lycomings in general have better distribution than continentals, While it may seem high, I would say that could be in a normal range. If it was injected, yes, worth investigating. Check for leaks at the flange on the intakes, they crack. Normally you see fuel stains but not always. You would have a lousy idle if they were cracked bad enough. In absence of obvious issues, change spark plugs, and have shop check valve lift to be on safe side. Could have low compression on those two . Carl
I heard that closing the throttle a tiny bit aids to distribute the fuel better, because the butterfly valve then creates turbulence. Maybe worth a try
You can also share the link to the entire flight on the savvy website – then people can dig through the other parameters.
For example, here is one of my recent flights.
https://apps.savvyaviation.com/beta/shared/flight/6626599/6ee9e6ec-2066-4eac-a32d-e77bceca1c34
We have very recently had Garmin EIS installed in our O-540 powered Piper Dakota (carbureted).
A very quick look at the engine data shows that the EGT diff varies a lot, but on several flights I see up to 230 F differences between the 6 EGTs. Sometimes the max difference is 100 F and sometimes less than 60 F. It seems to depend very much on engine setting, but I do not have the overall picture yet. On most flights there is a 200 F spread some of the time.
Conclusion: If a 150 F spread means that there is a serious issue with @duch_flyer’s O-360, then our O-540 must be almost falling apart.
No doubt that most carbureted engines have a terrible fuel distribution between cylinders, but EGT spread at any given power setting is not a very good indicator of that. For that, do the old GAMI lean test – to find the “GAMI spread”. Lots of references. The GI275 EIS does it semi-automatically, actually. Just go to the lean assist page (which I don’t use for leaning, by the way), and lean slowly. Once you are done, the GAMI spread is in the lower right corner of the screen. We are going to experiment with partial carb heat and other tricks to try to reduce the spread and make the engine run smoother when leaned.
I think there could be a number of reasons for large EGT differences, and I am not really ready to panic, as long as the engine is running smoothly and the other indications are ok. One problem, however, is that large EGT variations could mask anomalies, such as e.g. an EGT rise on one cylinder due to a spark plug failing.
